Key idea
Mass-energy equivalence
E = mc²
Einstein’s relation E = mc² expresses the equivalence of mass and energy. In reactions, a change in total rest mass corresponds to a change in energy.
Mass-energy equivalence
The key idea
Einstein’s relation E = mc² expresses the equivalence of mass and energy. In reactions, a change in total rest mass corresponds to a change in energy.
Why it matters
Nuclear reactions make this especially visible because small mass differences can correspond to substantial energies.
A picture to remember
Key idea
Mass-energy equivalence
Guided example
Mass-energy equivalence
Einstein’s relation E = mc² expresses the equivalence of mass and energy. In reactions, a change in total rest mass corresponds to a change in energy.
Put it into practice
Mass-energy equivalence
Choose a concrete case linked to Mass-energy equivalence. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.